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Effective SQL: 61 Specific Ways to Write Better SQL, First Edition by Ben G. Clothier, Douglas J. Steele, John L. Viescas

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4. Filtering and Finding Data

Perhaps the most important task you can do in SQL when attempting to turn the data found in one or more tables into useful information is look for data of interest or filter out data not of interest. Sometimes filtering involves matching an entire set of data with another entire set. Other times you accomplish filtering by testing for specific values in one or more columns. This chapter explores all the techniques you can use to find exactly the information you need from your database.

Item 22: Understand Relational Algebra and How It Is Implemented in SQL

Dr. Edgar F. Codd is widely recognized as the “father” of the relational model of database management. He introduced terms such as relation (a table or view), ...

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